Phenyllithium interconversion

Phenyllithium can be used in Grignard-type reactions involving attachment of phenyl group, eg, in the preparation of analgesics and other chemotherapeutic agents (qv). It also may be used in metal—metal interconversion reactions leading, eg, to phenyl-substituted siUcon and tin organics. 

Some unexpected reactions are observed during the interaction of cyclo-hepta[c]thien-6-one (231) or its 1,3-dibromo derivative and organometallic compounds (74YZ1429) These reactions are halogen-metal interconversion and subsequent dimerization, partial debromination, and simultaneous 1,2- and 1,4-addition of phenyllithium onto tropone 231 to yield tropylium salts 232 and 233, respectively (Scheme 56). 

TABLE 5. Thermodynamic (°) and Eyring activation (J) parameters for the interconversion of dimers, D, and monomers, M, of phenyllithium in THF-dg25 ... 

Halogen-metal interconversion sometimes occurs prior to the coupling reaction. " Thus, phenyllithium and benzyl bromide react to give bromo-benzene and bibenzyl rather than diphenylmethane. ... 

Halogen-metal interconversion—Retention of configuration s. 11, 731 Phenyllithium CgH Li... 

Halogen/metal permutation and hydrogen/metal permutation (usually apostrophed as "metalation") dominate the interconversion methods. They employ organoalkali reagents such as phenyllithium, methyllithium, -butyllithium, iec-butyllithium, or the superbasic LIC-KOR mixture. However, even if commercial, these reagents have to be made beforehand. The reaction of a chloro- or bromo-substituted hydrocarbon with lithium, sodium, or magnesium offers a standard entry to them. Thus, ultimately one always has to revert to the metal. 

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